Decidualization of uterine adenomyoma in a pregnant woman: a case report with immunohistochemical study.

Background: Decidualization of uterine adenomyoma has not been reported, to the best of the author's knowledge.

Aim: To report a case of uterine adenomyoma with decidualization.

Case Report: A 43-year-old pregnant woman with "myoma" underwent cesarean operation and "myomectomy" at 37 gestation weeks. The operation was successful, and the baby and mother were healthy. Grossly, the "myoma" measured 12 × 10 × 10 cm, and the consistency was firm. Microscopically, the tumor was adenomyoma consisting of smooth muscle bundles and endometrial islands. Characteristically, the endometrial stroma showed marked decidualization. An immunohistochemical study showed that the decidual cells were positive for pancytokeratin AE1/3, pancytokeratin CAM5.2, cytokeratin (CK)7, CK18, vimentin, CA125, CD10, estrogen receptor (ER), progesterone receptor (PgR), and Ki-67 (labeling 1 %). They were negative for CK34βE12, CK5/6, CK8, CK14, CK19, CK20, EMA, p63, desmin, α-smooth muscle actin, S100 protein, CK34, CD68, and p53. These results show that marked decidualization occurs in adenomyoma during pregnancy, and that the decidual cells are positive for pancytokeratin AE1/3, pancytokeratin CAM5.2, CK7, CK18, vimentin, CA125, CD10, ER, and PgR.

Conclusion: A rare case of uterine adenomyoma with decidualization is reported.